c:\@Work\Perl\monks\naderra>perl agct_substrings_1.pl
# all the following should be accepted
ok 1 - 'A,G'
ok 2 - 'AG,CT'
ok 3 - 'TC,CA'
ok 4 - 'GAT,CGA'
ok 5 - 'CGAT,TG'
ok 6 - 'CGAT,CTGA'
# all the following should be rejected
ok 7 - '': empty string
ok 8 - ' ': space
ok 9 - ',': comma, no sub-strings
ok 10 - ',G': missing 1st sub-string
ok 11 - 'G,': missing 2nd sub-string
ok 12 - 'ACGT': missing comma
ok 13 - 'X,A': incorrect character
ok 14 - 'AA,G': repetition of character in 1st substring
ok 15 - 'ACGTA,G': repetition of character in 1st substring
ok 16 - 'AC,GGC': repetition of character in 2nd sub-string
ok 17 - 'AC,ACGTA': repetition of character in 2nd sub-string
ok 18 - 'ATGA,TGG': repetition in both sub-strings
ok 19 - 'ATCXG,AAC': incorrect character and repetition
ok 20 - no warnings
1..20